Advanced Diesel Common Rail Sysems for Fuure Emission Legislaion Dr.-Ing. Ulrich Dohle, Dr.-Ing. Seffen Kampmann, Dr.-Ing. Jürgen Hammer, Dr.-Ing. Thomas Winrich, Dr.-Ing. Claus Hinrichsen (lecurer) Rober Bosch GmbH, Sugar, Germany ABSTRACT Wih he fuure emission legislaion challenging goals will be defined for Diesel engine manufacurers. Lowes emissions wih highes engine performance, low noise level, benchmarking low fuel consumpion and aracive coss are defining he arges of heir developmen aciviies for fuure engines. A fuel injecion sysem supporing hese requiremens will be a key facor. BOSCH launched very early a fundamenal sudy o invesigae he requiremens for fuure injecion sysems and heir key characerisics e.g. mixure formaion, maximum injecion pressure, rae shape capabiliy and muliple injecion. Using several versaile prooype injecion sysems a comprehensive engine invesigaion was accomplished o deermine he opimum sysem configuraion for he above menioned Diesel engine goals. Ou of hose overall sysem requiremens, he evoluion of Advanced Common Rail Technology could be defined. Key-words: Fuure Emission Legislaion, Concep Finding, Common Rail, Hydraulically Amplified Diesel Injecor INTRODUCTION The modern Diesel engine sill encouners a srong increase of is marke share in all passenger car segmens. Non-compeiive low fuel consumpion combined wih high power densiy and sporive specific orque provide Diesel cars wih an ousanding percepible fun o drive facor. On he oher hand, he Diesel finds iself more and more faced wih coninuously burdening challenges which have o be overcome wihin he echnical progress. Figure 1: Diesel Progress for Passenger Cars Drivers and Challenges While he gasoline engine seles he benchmark for noise vibraion harshness (NVH), he complexiy of he overall Diesel sysem becomes higher and higher in spie of he remendous desire o lower he overall sysem coss. The bigges challenge in Diesel applicaions is he fuure emission legislaion in mosly all markes over he world. To overcome his challenge an overall sysem opimisaion of he fuel injecion equipmen, he engine and combusion process and he exhaus gas reamen is mandaory. Facing he ask o realise a cos opimal soluion fulfilling he fuure emission legislaion, combusion noise comparable o gasoline engines, lowes fuel consumpion and fun o drive on op, appears o be an insolvable ask. The big effor in exhaus gas reamen for heavy passenger car vehicles o fulfil fuure emission legislaion leads o an unaracive low score for Diesel drive rain sysems. Ou of ha he engine ou emissions have o be reduced due o an overall Diesel sysem opimisaion. A promising approach is he air sysem, e.g. innovaive boos pressure conceps in combinaion wih high sophisicaed cooled exhaus gas recirculaion (EGR). Addiionally he adapaion of he combusion process, for insance he opimisaion of he pison bowl has shown a huge poenial.
Air sysem Combusion Nozzle Summarising he requiremens on he desired advanced fuel injecion equipmen one will find again he well-known keywords of a sandard Common Rail sysem like: Saring poin of opimizaion EGT Injecion sysem fully flexible injecion pressure maximum required injecion pressure, dependan on he specific concep flexible iming of muliple injecions and small and sable injecion quaniies o realise pilo and pos injecions. Addiionally he research leads o some new characerisics according o Figure 2: Diesel Sysem Opimisaion Areas Las bu no leas he advanced fuel injecion equipmen plays a key role o achieve fuure Diesel goals. The examinaion of he overall sysem requiremens and deriving ou of hem possible soluions will be discussed in he nex chaper. SYSTEM REQUIREMENTS FOR FUTURE FIE The idea of overall sysem requiremens evaluaion is shown in figure 3. Based on he behaviour of wellknown fuel injecion equipmen, he mos imporan parameers o idenify he required injecion performance could be separaed and evaluaed. The nex sep leads o prooype injecion sysems which show all specific working behaviour corresponding o he iniially menioned parameers. Sensiiviy analysis of imporan injecion parameers for he engine performance Feaure: Pressure a he needle Needle lif 1 2a 1 Pilo injecion (number, ime gap, quaniy, olerance) 2 Opening pressure, influence of pressure ramp, gradien 3 Max. injecion pressure, influence of small nozzle holes 4 Pressure gradien during closing 5 Pos injecion (near, lae, influence of pressure level) 6 Opening and closing speed of he needle 2b 6a 3 max. injecion pressure Figure 3: FIE Requiremen Evaluaion 6b 4 5 Time The prooypes were designed as pressure and sroke - conrolled injecion sysems and hybrids ou of hem. Those prooypes were esed using an opimised Euro4 combusion process for passenger cars and ligh duy applicaions. Those were calibraed for an equal power densiy by means of he absolue nozzle flow rae. Goal of he opimisaion was he bes radeoff in soo vs. NOx while fuel consumpion was held as consan and noise arges could be reached. fas needle opening low injecion rae during igniion delay, bu max. allowed injecions rae o increase he local air raio srong increase of he injecion rae afer sar of combusion high maximum injecion rae fas rae decrease a he end of injecion and also high needle closing velociy. To solve his conflic he whole poenial of modern fuel injecion equipmen has o be kep in mind and is basically needed. The invesigaions show, ha a full flexible rae shape in he whole engine map leads o he required performance. Opimal Rae Shape @ Par Load Injecion Rae very fas needle Igniion fla slope slow increase seep slope seep drop fas increase fas decrease Elapsed Time Figure 4: Opimal Rae Shape for PC-car engines These findings on he demand for an opimum FIE behaviour led o he concep finding sage. Already a an early sage wo possible main sreams urned ou o be promising: a furher increase in rail pressure ogeher wih very small hydraulic nozzle flow raes based on he Piezo Inline injecion concep and an appropriae rae shaping ou of hydraulic pressure modulaion, he so-called Hydraulically Amplified Diesel Injecion Sysem (HADIS). ADVANCED COMMON RAIL SYSTEMS Figure 5 gives a brief overview on he produc porfolio of BOSCH Common Rail Sysems. Beside he
already successful launched Common Rail generaions CRS1, CRS2 and CRS3, i is planned o exend he available performance of fuel injecion equipmen o he OEM by exending he pressure level of he 3 rd generaion Piezo Inline Common Rail up o 2.000 bar. Addiionally, on he op - end of Common Rail, he synhesis of pressure conrolled injecion sysems and Common Rail is done by providing he 4 h generaion of Common Rail wih he highes pressure level of 2.500 bar and passive rae shaping. High Level Pressure wih Pressure Amplificaion EDC17C 2000 bar High Performance Piezo-Inline Injecor Piezo-Inline-Injecor 1600 / 1800 bar Fuel meered high pressure pump wih improved performance EDC16C-P / EDC16C+ Opimized SV-Injecor Muliple Injecion (4-5) Fuel meered high pressure pump EDC16C Innovaion CRS1 1.350bar CRS2 1.600bar CRS3.0 1.600bar CRS3.2 1.800bar BOSCH sae of he ar CRS4 2.500bar CRS3.3 2.000bar 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Figure 5: BOSCH Common Rail Roadmap By realising he Piezo - Inline - design in he 3 rd generaion of Common Rail, BOSCH did really mainain he abiliy of Piezo acuaing in a Diesel injecion sysem. recangular shape. This mainains a higher power oupu a raed poin of he engine, while reducing he nozzle flow rae provides big seps in using he high pressure o realise an opimal spray formaion. Sake in pull down he emissions and improving fuel consumpion can be earned a he end of he engine calibraion process. Finally he small flow rae leads o a reduced amoun of prepared mix during igniion delay, herefore combusion pressure gradien flas down o give a smooh combusion noise frequency paern. From durabiliy poin of view he high sress pars of he injecor and nozzle, naurally he whole sysem componens, have o be qualified o he higher rail pressure level of 2.000 bar. Anyway, from engine mouning poin of view i migh be an imporan issue ha compaibiliy o he series sysem, CRS3.0 wih 1.600 bar, is fully given. CRS4: HIGH PRESSURE CONCEPT - HADIS The second concep invesigaed employs a furher increase of he injecion pressure uilising he Hydraulically Amplified Diesel Injecion Sysem (HADIS). An injecion pressure in he nozzle hole area of 2.500 bar is realised. Figure 7 shows he hydraulically amplified injecor CRI4 wih is main opics. Due o he fac, ha a very siff acuaion chain, from energising he Piezo sack down o he needle conrol, he near posiion of he sack o he conrol valve leads o he desired needle kineics of he nozzle. This working principle will be exended o be driven by higher pressure levels, figure 6. Figure 7: 4 h Gen. Common Rail Injecor CRI4 Figure 6: 3 rd Gen. Common Rail Injecor CRI3 To say on very small injecion quaniies and fully flexible muliple injecion evens, he layou opimisaion of injecion dynamics wih he higher pressure level is used. On he one hand a full load he injecion rae could be moved o a nearly perfecly Thus high specific power oupu can be achieved even wih very low nozzle flow raes. The pressure amplifier is hydraulically driven wih a geomerical ransmission raio of roughly 1:2 allowing a moderae high pressure level on he pump and rail side of up o 1.350 bar. This helps a lo in reducing he mechanical sress on he componens, because only he nozzle module has o be designed for he highes pressure range. On he oher hand he delivery rae of he high pressure pump has o be significanly increased o supply he necessary conrol quaniy o drive he pressure amplifier.
The imporan parameers ou of he requiremen evaluaion for advanced FIE are realised in he injecion behaviour of he CRI4. Namely he ramp rae shape is characerisic for he CRI4 concep. A par load i enables o overcome he conflic beween emission and noise and a full load he approach o he square shape provides he capabiliy o injec he necessary fuel quaniy o reach he specific power goal. The change of rae shape comes ou of he specific hydraulic layou of he injecor concep wih only one elecronic acuaor and is called passive rae shaping. Load needle lif p pump. Figure 9 shows he CP4 wih heir main design opics. The CP4 - concep of a cam drive uni is compleely differen o he already launched Common Rail high pressure pumps of he whole world marke. Derived from he successful disribuor pump VP44, a double cam drives a roller appe which moves he high pressure plungers o pressurise he fuel inernally. The whole high pressure area is locaed in seel heads which also conain he high pressure elemen, sucion and check valves. This avoids all inernal high pressure lines, so he housing of he CP4 is designed o be made of aluminium. The pressurised fuel leaves he pump hrough wo high pressure lines direcly conneced o he rail. Summarising he CP4 key issues, one leads o p rail Maximum high pressure up o 1.800 bar and high efficiency in he whole pump map, offering he poenial for a furher pressure increase. Figure 8: Passive Rae Shaping Speed These characerisics combined wih a very high injecion pressure leads o valuable benefis especially a high load condiions. Therefore he 4 h generaion Common Rail Sysem suis opimal for LD and heavy passenger car applicaions in Europe and he US. COMMON RAIL HIGH PRESSURE PUMP CP4 As already successfully launched for 1 s and 2 nd generaion of BOSCH Common Rail sysems he high pressure pump CP4 is also designed as a radial pison pump. Reduced rail pressure ripples achieved by a high qualiy for he equal and synchronous delivery allowing improved meering accuracy of he injecors Flexible range of applicabiliy in modern BOSCH Common Rail Sysems wih long erm sandardisaion of he high pressure pump inerface o he engine The CP4 is engineered as a plaform produc offering differen marke oriened designs. The CP4 plaform mainains he opimal scaling of a specific pump ype o he required Common Rail sysem funcionaliy for differen applicaions. For example working wih he 3 rd generaion Common Rail Sysem one obains he need of high pressure and less quaniy using he Piezo Inline injecor sysem; vice versa in case of Common Rail 4 h generaion due o he bigger quaniy amoun of he CRI4 while driving he pressure amplifier a moderae pressure level. POTENTIAL EVALUATION OF MODERN COMMON RAIL SYSTEMS Figure 9: Common Rail High Pressure Pump CP4 Furhermore he inake sucion conrol achieved by a meering uni was ransferred o he high pressure pump CP4. Depending on he specific applicaion here is he opion of a mechanical or an elecrical supply As discussed in he previous chaper he advanced FIE echnology of fuure Common Rails Sysems from BOSCH shows a clear beneficial performance increase of he foreseen FIE - generaions. On he oher hand due o he high echnical value of he sysems a cerain addiional effor is expeced by means of an overall cos penaly. Under ha challenge he discussion moves very fas o he quesion of opimisaion in erms of benefi versus effor of he sub sysems of he whole Diesel drive rain, namely FIE and exhaus gas reamen equipmen. The quesion comes up for a sraegy o find an opimal sysem configuraion for
each vehicle class in a specific marke o reach he emission and performance goals wihin an overall cos minimum. Figure 10 illusraes ha opimisaion ask in a very impressive way. Diesel Sysem Opimizaion Very powerful soluions are given wih he 3 rd and 4 h generaion of BOSCH - Common Rail Sysems because heir layou mainains a modern Diesel engine o reach power goals up o 70 kw/l. Simulaneously, hese FIE play an imporan role by undershooing fuure emission limis in Europe, wihou any addiional DeNOx - measure for compac class vehicles. Euro 5* Esimaion, Vehicle Tes Weigh: 1400 kg Vehicle mass kw/l EGT EGT=exhaus gas reamen FIE= fuel injecion equipmen FIE NO x g/km 0,20 0,15 0,10 0,08 25 % 55 % Euro 4 - engines 0,14 50 % 0,12 0,10 35 % Eng. Goal Euro 5 - engines low ε, TC 2, phcci... Scenario 1: Euro 5 Scenario 2: Figure 10: Overall Diesel Sysem Opimisaion Here balance disurbances caused by he vehicle weigh or he power oupu are compensaed by he performance of he FIE and he exhaus gas reamen sysem in order o lower emissions. Sill uilising a convenional combusion sysem, however, opimised for lowes raw emissions and based on he calculaion of such a balance firs answers can be given on he following wo quesions: Wha kind of effors on he FIE and exhaus gas reamen side are necessary o mea he emission and performance goals for a specific vehicle applicaion in Europe? Is here a way o reduce he effor on he exhaus gas reamen side generally employing a sophisicaed FIE? Uilising modern Diesel engines wih he described Advanced Common Rail Sysems from BOSCH leads o he answer of he asked quesions for all markes and heir oday s and fuure emission legislaion. The firs general finding is, ha he beer he FIE performance ges, he lower he effor on he exhaus gas reamen side remains. I depends on he assessmen of he combusion specialis wheher he assumes o achieve he fuure emission goals wih he sophisicaed solenoid driven injecion sysem CRS2.2 or he migh need o sep ino he Piezo echnology of he 3 rd generaion of BOSCH Common Rail. This answer canno be given in general and is a srong funcion of he specific power goal, he displacemen of he engine and of course of he vehicle ineria mass. 0,05 Eng. Goal 35 % base CRS 3 * sill under discussion CRS 4 CRS 4 wih DPF NSC Figure 11: Esimaion of FIE - Emission Poenials CONCLUSIONS Summarising he siuaion he bigges challenge in Diesel echnology for he fuure is he fulfilmen of coninuously srenghened emission arges. BOSCH will coninue suppor o mee he challenges by supplying advanced fuure FIE echnology. Derived from an overall sysem requiremen evaluaion o fulfil fuure performance arges of he Diesel he key requiremens for fuure Common Rail sysems were idenified. The resuls from an engine based sudy using various prooypes of injecion sysem conceps for advanced FIE, engine measures and exhaus gas reamen equipmen lead o he pah for echnical soluions for fuure emission legislaion. The required effor on he FIE and he exhaus gas reamen for passenger cars srongly depends on he ineria vehicle weigh, he power oupu and he chosen engine displacemen. In erms of an overall opimisaion i has o be saed, ha he inves on he FIE has a big impac on he reducion of he exhaus gas reamen effor o ge home wih he projec fulfilling fuure emission arges a a sysem cos minimum.